In general, a drum-type washing machine has the dual functions of washing and drying laundry.
FIG. 1 shows a configuration a drum-type washing machine. It includes a dryer 30 configured to capture moist air from a tub 20 and return high-temperature and dry air back into the tub 20. The tub 20 includes a drum 21 for accommodating laundry.
The dryer 30 includes a condensing duct 40 with one side coupled to the tub 20; a blast fan 50 coupled to the other side of the condensing duct 40; and a drying duct 60 with one side coupled to the condensing duct 40 via the blast fan 50 and the other side coupled to the tub 20. The drying duct 60 includes a heater 70 embedded therein. The moist air in the tub 20 is captured into the condensing duct 40 and is condensed and turned into low-temperature dry air. The condensed low-temperature dry air is transformed into high-temperature dry air by the heater 70 within the drying duct 60. The high-temperature dry air is then introduced into the drying duct 60 via the blast fan 50 and supplied back to the tub 20.
FIG. 2 is a diagram illustrating the configuration of a condensing duct 40 in a conventional drum-type washing machine 10 shown FIG. 1. Damp air flows from the tub 20 to the condensing duct 40 through an inlet 41 and comes into contact with cooling water flowing in the condensing duct 40. The damp air is cooled off by the cooling water and thus condensed. The damp air with reduced humidity is discharged to the drying duct 60 through an outlet 42 and the blast fan 50.
In the condensing duct having the above-described structure, the contact time between the air and the cooling water may not be long enough to allow the air to be condensed sufficiently. To solve this problem, Korean Patent Laid-open publication No. 10-2012-0073583 discloses a technique of improving the drying effect by providing a bypass to increase a contact time between air flowing within the condensing duct and cooling water supplied into the condensing duct. The drawback to this technique is that the air and the cooling water come into direct contact with each other, and the cooling water may be drawn into the drying duct when the air is sucked into the drying duct from the condensing duct by the blast fan. However, the cooling water vapor may cause unwanted corrosion of various components, such as the blast fan, the drying duct and other components. Furthermore, the vapor may return to the tub through the blast fan and the drying duct and consequently counteract the drying efficiency.